Treating a permeable mass



Dec. 27, 1966 c. BEZEMER ETAL. 3,294,168

TREATING A PERMEABLE MAss 2 Sheets-Sheet 1 .SLUO/V DRIVE F/ OTHER STRATAFiled April 2o. 1964 on. olsPLAclNG LIQUID SPACER LIQUID FIG. I

OIL TAKEN FROM FORMATION OTHER STRATA FIG. 2

INVENTORSI CORNELIS BEZEMER FRANCISCUS H. MEIJS MARINUS VAN ZANTEN BY:M41@ /in THEIR ATTORNEY Dec. 27, 1966 `Filed April 20, 1964 C. BEZEMERETAL TREATING A PERMEABLE MASS 2 Sheets--Sheaei 2 NON POROUS FORMATIONSING FORMATION NON-POROUS IIT FORMATIONS FIG. 3

INVENTORS'.

CORNELIS BEZEMER FRANCISCUS H. MEIJS MARINUS VAN ZANTEN BY: QM

THEIR ATTORNEY United States Patent 3,294,168 TREATING A PERMEABLE MASSCornelis Bezemer, Franciscus H. Meijs, and Marinus van Zanten, all ofRijswijk, Netherlands, assignors to Shell Oil Company, New York, N.Y., acorporation of Delaware Filed Apr. 20, 1964, Ser. No. 361,111 Claimspriority, application Great Britain, Apr. 22, 1963, 15,777/ 63 7 Claims.(Cl. 16o-33) This invention relates to a method for treating a permeableearth mass. According to this invention, use is made of an epoxycompound which on hardening either fills the pore space of the permeablemass or forms a film covering the walls of the pore space of said mass.The earth mass treated according to this invention may be originallyconsolidated, partly consolidated or unconsolidated. It may be .aboveground or underground.

The method according to the invention wherein the hardened epoxycompound lls the pore space of a permeable mass may be applied forplugging purposes in case the mass is to be tight against the passage offluids, which is often required in dams or dikes, in holes dug in theground, or to close the communication between a subsurface formationcontaining oil, water or gas and the interior of a well or mine-shaftpenetrating such formation. It may be employed for foundation purposes,wherein the strength of a mass has to be improved, for example, tostrengthen the subsurface soil below buildings, or at the lower ends ofpiles.

In the method according to the invention wherein the hardened epoxycompound forms a film covering the walls of the pore space of apermeable mass, the original permeability of a mass is substantiallyretained; this method is, therefore, particularly suitable to provide abond between the loose grains of a subsurface formation which ispenetrated by a well, to prevent the grains from being entrained byfluid passing into or out of the formation. In particular when such awell is used as a production well for producing gas, water or oil from asubsurface formation, considerable damage can be done to the productionequipment by those grains which are carried by the uid ow to the wellhead, while the coarser grains, which accumulate in the producingsection of the well, can reduce the wells production rate to such anextent that it is not possible to produce the well economically.Consolidation according to this invention can completely prevent suchsand damage.

This invention will be illustrated by reference to 'the attacheddrawing, wherein:

FIG. l is a vertical section through a well borehole, diagrammaticallyillustrating the injection of a resin solution into a formation for sandconsolidation with retention of permeability;

FIG. 2 is a vertical section through the same well borehole shown inFIG. l, illustrating the production of oil from the treated formation.

FIG. 3 is a vertical section through a well borehole, illustratinginjection of resin solution into a formation for purpose of plugging.

This invention is especially useful in the consolidation ofunconsolidated sand formations surrounding the boreholes of oil wells.The remainder of the description therefore will be largely directed tosuch sand consolidation.

One of the requirements of a good consolidation method is that it can beapplied at the various temperatures which are to be expected in theformations. Further, it is required that the bond formed by the hardenedresin between the particles or grains of the formation will be resistantto formation iuids and/ or to chemicals injected Mice into theformation, as well as to movements in the neighboring unconsolidatedparts of the formation. On the other hand, the amount of resin requiredto give the formation the necessary mechanical strength should notexcessively impair the permeability thereof, so that a flow of fluidsfrom the formation to the well, or vice versa, will remain possible.This is of utmost importance when consolidating formations having a lowpermeability. This invention meets the stated requirement for a goodsand consolidation method.

Various resins have been employed in lattempts to provide satisfactoryconsolidation of sand-producing formations. This invention provides animprovement of a recently developed and commercialized method whichcomprises the steps of (a) Preparing a solution of an epoxy compound andone of certain curing agents in a hydrocarbon solvent;

(b) Injecting the solution into the pore space of a suitably preparedearth mass or formation; and

(c) Retaining the solution in the mass for a sufficient time to permitan intermediate resinous product to separate from the solution, depositon the particles of the mass and cure to a hard, cross-linked resin, orfor the whole solution to gel and fill the pore space.

One of the advantages of said method and of this invention over the useof phenolic resins and over some previously described methods ofutilizing epoxy resins for the consolidation of earth formations is thatall reactants required to produce the resinous cement are present in asingle batch of liquid. As will be described hereinafter, it isdesirable to pretreat the formation to be consolidated with awater-displacing liquid, if desired preceded by an oil-displacing liquidand followed by a spacer liquid. These do not exert any significantchemical action on the earth formation, serving merely to remove anyunbound water from the formation. A spacer liquid may not be needed, forexample, when the water-displacing liquid is compatible with the resinsolution.

A particularly desirable aspect of said method and of this invention isthat the amine not only serves as curing agent but also has the propertyof imparting surfactant characteristics to the partially cured resinwhich precipitates from solution, causing said resin to preferentially:adhere to grains of the formation. The amine is preferably employed inat least 5% molar excess over the amount stoichiometrically required toreact with all the epoxy groups of the uncured epoxy resin. By preparingthe resin-amine solution in this manner the bond between precipitatedresin and the sand grains of originally waterwet earth formation isgreatly improved.

If precipitated resin were present in the solution when it reaches theformation it would tend to cause the undesired effects described above.It is, therefore, an important aspect of said method and of thisinvention that the solution is prepared in a controlled manner toprevent any precipitation of solid resin prior to the time the solutionis completely injected into the formation to be treated. This isaccomplished by selecting the type and/or concentration of thecomponents of the resin-forming solution in a manner describedhereinafter in greater detail, and by preventing contact of thesolution, prior to injection into the formation, with materials whichwould, precipitate resin therefrom.

A significant distinctive characteristic of said method and of thisinvention as applied to sand consolidation is that properly composedtreating solutions can retain partial reaction product of polyepoxideand amine in solution until the treating composition is placed in theformation, and thereafter permit partially cured product to separate asa viscous, insoluble liquid phase which preferentially wets sand grains.Solutions of other resin at such a stage of partial curing tend to formgels which do not selectively wet the grains of the formation and henceare not able to result in a treated formation which still retains themajor proportion of its original premeability to oil. Also, formationstreated according to this invention, in which resin cementing takesplace at the contact points of the individual grains of the formation,are stronger than similar formations treated by other methods.

The period elapsing between the moment of preparation of the solutionand the moment at which the first droplets of resin separate from thissolution or the first evidence of gelling is observed is called theInitial Resin Separation time; this will be referred to hereinafter asIRS time.

So as to prevent plugging of the area over which the solution enters themass, the solution has to be injected into the mass before gelling or`separation of resin droplets therefrom. It will be clear that the IRStime has to be longer than the time required to pump the solution fromthe spot where the solution has been prepared into the mass which is tobe treated.

As the IRS time is shortened by an increase of the temperature underwhich the reaction between the epoxy compound and the curing agent takesplace, diiculties when treating high-temperature masses (such asformations lying at great depths) are often encountered,specificallywhen long injection periods are required, eg., when treatingmasses having low injectivity. small, unexpected delay in the pumpingoperation when transporting the solution down the hole to the formationto be treated will result in a separation of resin from the solution orgelling of the solution before the solution has entered the formation.The resin then plugs the pores of the area over which the solutionshould enter the formation. Consequently the pressure required to injectthe solution into the formation rises above the working pressure of theinjection pumps, which stall, leaving the solution in the well, wherethe resin hardens in situ. A new attempt to treat the formation can beundertaken only after removal of the hardened resin plug deposited 4 onthe wall of the well and in the well bore.

This invention now provides a method for utilizing in the above-outlinedearth-treating method lower aliphatic ketones which result in unusuallylong IRS times and consequently allow the treatment of formations whichare at a greater depth or have a higher formation temperature or a lowerinjectivity than formations which could be treated by previouslyavailable methods.

The method for treating a permeable mass according to this inventioncomprises the steps of:

(a) Preparing a solution of a resin-forming expoxide having more thanone vicinal epoxy group per molecule, one of certain curing agents forsaid epoxide, and a lower aliphatic ketone, in a highly aromatichydrocarbon solvent, characterized by preferential solubility for theintermediate resin product so as to keep dissolved the amount ofintermediate resin product formed during the time required to pump saidsolution into an earth formation to be treated; Y

(b) Injecting the solution into the pore space of a suitably preparedpermeable earth mass or formation; and

(c) Retaining the solution in mass for a sufficient time to permit anintermediate resinous product to form, separate as a liquid, and depositon the particles of the mass or for the whole solution to gel and fillthe pore space,

'and for the intermediate resin to cure to a hard, crosslinked resin.

The porosity and permeability of the formation to be vtreated permitestimation of the amount of surface area that should be contacted by thecured resin. The concentration of the resin components (epoxy compoundand curing agent) is selected to form a solution containing at least 3and preferably between 5 and 50 percent by volume of resin components,at least suicient to contact substantially all of the surface area inthe portion of Then even a formation to be impregnated by the solution.The range below about 20 percent by volume is generally employed whenthe permeability of the formation is to be retained in substantial part,and the range above about 20 percent when plugging is desired. Thesolution is preferably adjusted to retain a viscosity below 100centipoises at formation conditions COMPONENTS USED IN THE TREATINGPROCESS Solvents The solvents in which the polyepoxide and curing agentare dissolved to prepare the resin solutions used in this invention arehydrocarbon solvents containing a substantial proportion of aromatichydrocarbons, preferably at least 50% by weight. The solvent may be asingle aromatic hydrocarbon or a mixture of aromatic hydrocarbon withsaturated non-aromatic hydrocarbons. Suitable aromatic hydrocarbons arebenzene or benzene derivatives, e.g., alkyl benzenes such as toluene,xylenes and the like. Other suitable aromatic hydrocarbons are thoseobtained by extraction of aromatics from kerosene, gas oil, spindle oil,lubricating oil or heavy catalytically cracked cycle oil. A particularlyuseful aromatic cornposition is a kerosene extract boiling in the rangefrom 350 to 510 F., eg., an SO2 kerosene-extract of API gravity 25-28,an initial boiling point between 350 and 390 F., an end point between450 and 510 F., and an aromatics content of at least by weight, theremainder being saturated non-aromatic hydrocarbons. The polyepoxidesolution may be prepared from such aromatic solvent with admixture ofhydrocarbons containing a greater proportion of non-aromatics, e.g.,unextracted kerosenes, gas oils or the like. In general, oils boilingabove 175, and preferably between 350 and 650 F. are employed assolvents herein.

The ratio of aromatic to non-aromatic hydrocarbons in the resin solutionaffects the IRS time of the solution. For example, decreasing the volumepercentage of aromatics in a resin solution from 87 to 71.5 percentreduces the IRS time at otherwise equal conditions by one third.

The ratio of aromatic to non-aromatic hydrocarbons is one of the majordeterminants of the state in which resinseparation takes place. Theother major determinant is the total concentration of resin-formingingredients. Solutions in which the aromatics oontent of the hydrocarbonsolvent is over 90% by weight tend to gel, rather than permitting theresin to separate out as a separate phase, when the concentration ofresin-forming ingredients is between 20 and 50 percent by volume of thesolution.

Polyepoxides The polyepoxides used in the process of the inventioncomprise those organic materials possessing more than one vic-epoxygroup, i.e., more than one group. These materials may be saturated orunsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic. Theyare referred to herein as resin-forming epoxides or as polyepoxides. Inthe art, even the uncured materials are often referred to as epoxyresins.

Po'lye-poxides can be described in terms of epoxy equivalent value,whic-h refers to the nu-mlber of' epoxy groups contained in the averagem-olecule. The meaning of this expression is described in U.S.2,633,458. I-f the polyepoxide consists of a single compound and all ofthe epoxy groups are int'act, the epoxy equivalency will be an integer,such as 2, 3, 4 and the like. However, in the case of polymericpolyepoxides many of the materials may contain some of the monomericmonoepoxides or have some of their epoxy groups hydrated or otherwisereacted and/ or contain macromolecules of somewhat different molecularweight so that epoxy equivalent values, though greater than 1.0, may bequite low and may be fractional. The polymeric lmaterial may, forexample, have epoxy equivalent values such as 1.4, 1.8, 2.5 and thelike.

Polyepoxides suitable fo-r conversion to cured epoxy -resins arewell-known materials of commerce. Many are described in the book EpoxyResins by Lee and Neville, McGraw-Hill, New York, 1957.

Examples of vsuch polyepoxides are the epoxy polyethers of polyhydricphenols obtained by reacting a polyhydric phenol with ahalogen-containing epoxide or dihalohydrin in the presence of |analkaline medium. Polyhydric phenols that can be used for this purposeinclude, among others, resorcinol, catechol, hyd-roquinone, methylrescrcinol, and polynuclear phenols such as 2,2-bis(4 hydroxyphenyl)propane (Bisp-henol A), 2,2-bis(4'hy droxyphenyDibutane,4,4dihydroxybenzophenone, bis(4- hydrox'yphenyDethane,2,2-bis(4-hydroxypheny1)pentane, and 1,5-dih-ydroxynaphthalene. Thehalogen-containing epoxides may be further exemplified by3-chloro-1,2epoxybutane, 3-bromo-1,Z-epoxyhexane,3-chloro-1,2ep0xyoctane, and the like.

The monomer products produced by this method from dihydric phenols `andepichlorohydrin may be represented by the general for-mula wherein Rrepresents a divalent hydrocarbon radical of the fdihydric phenol. rIlhepolymeric products will generally not be a single .simple molecule butwill be a complex mixture of glycidyl polyethers of the general formulawherein R is a divalent hydrocarbon radical of the dihydric phenol-and nis an integer of the series 0, 1, 2, 3, etc. While for any singlemolecule of the polyether n is an integer, the Ifact that the obtainedpolyether is a mixture of compounds causes the determined value for n to.be an average which is not necessarily zer-o or a whole number at notedabove.

The aforedescribed preferred glycidyl polyethe-rs of the dihydricphenols are prepared in known manner by reacting the requiredproportions of the dihydric phenol and the epichlorohydrin in analkaline medium.

referred members of the above-described group of polyepoxides .are theglycidyl polyethers of the dihydric phenols, and especially of2,2-bis(4hydroxyphenyl)propane, having an epoxy equivalency !between 1.0and 2.1, preferably at least 1.4, a molecular weight between 250 and900, and a Durrans Mercury Method softening point preferably no 1greaterthan 30 C. Most preferred are the normally liquid products having amolecular weight of about 350 to 4G() and an epoxy equivalent of about1.75 to 2.1, and typically about 1.85, which may be prepared asdescribed Iunder the heading Polyether A in U.S. 2,633,458.

The glycidyl polyethers of polyhydric phenols obtained by condensing thepolyhydric phenols with epichlorohydrin as described above are alsoreferred to as ethoxyline resins. See Chemical Week, vol. 69, page 27,for September 8, 1951.

Another group of polyepoxides that may be used comprises the glycidylethers of novolak resins, which resins are obtained iby condensing analdehyde with a pollyhydric phenol. Typical members of this class arethe epoxy resins from formaldehyde 2,2-bis(4-hydroxyphenyl)pro panenovolak resin.

Curing agents The curing agents to he used to combine with theabove-described polyepoxides in the process of the present y and thelike.

6 invention are hydrocarbon-soluble amines which Iact both to impartpreferential .sand grain-wetting properties to the partially cured resinproducts, and as curing agent to-.convert the polyepoxide to aninsoluble infusib-le form.

Preferred in this invention are hydrocarbon-soluble polyaminespossessing one or more -membered carbocyclic ring, i.e., cycloaliphaticor aromatic rings. These include 1-cyclohexylamino-3-alminopropane,1,4-diaminocyclohexane, 1,3-diaminocyclopentane, ibis(3-methyl4aminocyclohexyl methane, bis( 4-aminocyclohexyl methane,di(arninocyclohexyl)sulfone, 1,3-di(aminocyclohex yl)propane,4-isopropyl-1,Z-diaminocyclo-hexane, 2,4-diaminocyclohexane,N,Ndiethyl1,4-diaminocyclohexane, Preferred members of this groupcomp-rise those polyafmines having at least one amino oralkylsubstituted amino groupattached directly to a cycloaliphatic ringcontaining from 5 to 7 carbon atoms. Especially suitable arehydrogenated primary and secondary aromatic polyamines having at leasttwo aminohydrogens, at least 50% of their aromatic structure having beenconverted to cy-cloaliphatic structure during hydrogenation. Thesecycloaliphlatic amines are preferably obtained lby hydrogenating thecorresponding aromatic amine. Thus di(aminocyclohexyl)methane isobtained by hydrogenating methylene dianiline. Use of these amines isdescribed in further detail in U.S. 2,817,644 to S'hokal et a-l. Theseamines Pare especially preferred because they react relatively `slowlywith the preferred epoxides in hydrocarbon solution. When used inconjunction with ketone curing reaction retarders they provide ampletime for the solution to be pumped into the earth formation to betreated, even in deep wells and those most resistant to injection offluid.

Suitable for use particul-arly at relatively high temperatures arearomatic polyamines, such as 1,3-diaminobenzene, 1,4-diaminobenzene,.4,4diaminodiphenyl and 1-pheny1amino-3-aminopropane, provided they aresoluble in the desired hydrocanbon solvent.

Other, generally less preferred amines include, among others, thealiphatic polyamies, such as, for example, propylene diamine, hexylenediamine, diethylene triamine, triethylene tetramine, tetraethylenepentarnine, 1, S-diaminobutane and hexamethylene diamine.

Other suitable, though less preferred amines are theN-(arninoalkyl)piperazines, such as, for example, N-aminobutylpiperazine, N-aminoiscpropyl-3-butoxypiperazine,N-aminoethylpiperazine, 2,5-dibutyl-N-aminoethylpiperazine,2,5-dioctyl-N-aminoisobutylpiperazine and the like, and theN-(aminoalkyDpiperazines wherein the alkyl group in the aminoalkylportion of the molecule contains 2 to 6 carbon atoms, and the totalmolecule contains no more than 18 carbon atoms.

Cure rate modifiers The rate of the 'curing reaction betweenpolyepoxides and amines in preponderantly aromatic hydrocarbon 'solutionis relatively slow .even without addition of cure rate retardingmodifiers. It has no'w been found that admixture of lower aliphaticketones to the resin-forming polyepoxide-amine solution in predominantlyaromatic hydrocarbons permits prolonging the IRS time to such an extentthat treatments requiring unusually long IRS times can be carried out.The ketone is preferably acetone, but other ketones of from 4 to 7carbon atoms per molecule, may be employed, eg., methyl ethyl ketone,methyl propyl ketone, diisopropyl ketone, or methyl isobutyl ketone.concentration in the range from 0.1 to l() volume percent -of thesolution, and preferably in the range from 2 to 5 percent. For areaction mixture, in a given hydrocarbon solvent, or a given polyepoxideand a lgiven curing agent lthe type and amount of ketone can be selectedto provide a desired IRS time.

It is sometimes advantageous to employ a phenol, eg., for the purpose offavorably influencing the completeness of separation of partially curedresin from the solution.

The ketone is generally employed in a Since a phenol at the same timeacts as cure rate accelerator, a greater proportion of ketone is thenrequired for a given extension of IRS time than is required in theabsence of phenol. The proportion of phenol may be from 0.1 -to 4%volume, basis solution. It is an advantage of this invention thataddition of ketones permits the beneficial effects of phenol addition tobe retained even where the cure rate accelerating effect of phenol, ifused alone, would make it necessary to omit it from the reactionmixture.

Crude oil displacing fluids If the formation to be treated is anoil-bearing one, it may be advantageous to first displace crude oil fromthe formation. This may be done with any hydrocarbon fluid of reasonablylow viscosity, e.g., a kerosene, diesel oil, or other middle distillate,which is miscible with the crude oil in the formation.

Water displacing fluids When consolidating part of an undergroundformation which contains connate water, i.e., liquid water adhering tothe grains of the formation due to capillary forces,v

it is usually preferred to remove such connate water before injectingresin solution into the formation. Several types of water-removingfluids may be employed for flushing connate water from a formation. Thewaterremoving fluid may be an oil solution of a surfactant. A preferredsurfactant for this purpose has the formula R -NH-(CH2)3-NH2, wherein Ris an alkyl group derived from coconut oil, soya oil or tallow. Adifferent group of suitable water-removing fluids are ketones andalcohols having less than 6 C-atoms per molecule, e.g., acetone, methylethyl ketone, methanol, ethanol or isopropanol.

Spacer fluids A spacer fluid may be employed between the waterdisplacingfluid and the resin solution. Such a spacer uid serves, i.e., to preventuntimely precipitation of epoxy resin. Suitable lspacer fluid is solublein the resin solution and non-reactive with the ingredients thereof.Suitable spacer fluids are, in general, the hydrocarbons used assolvents in the polyepoxide solutions. The spacer fluid may have `anon-uniform composition. For example, the predominant part, first pumpedinto the formation, may be a diesel oil, while the final part contains asubstantial admixture of an aromatic hydrocarbon.

Drive fluid In the process of this invention, each of the abovementionedpre-treating fluids is directly followed by the next one, so that thelatter serve as drive fluids for the former. The resin solution directlyfollows the last pretreating fluid.

Some care must be exercised in selecting a drive fluid for the resinsolution. kept in the part of the formation to be consolidated until thereaction is completed, the injection of the drive fluid should beinterrupted as soon as all the resin solution has entered the formation.Care should be taken that the solution or partthereof does not remain inthe welll as otherwise an impermeable epoxy resin sheath will be formedon the formation face, which will prevent the passage of fluid out ofthe formation into the well or vice versa. It is equally important,however, to make sure that the solution is not driven too fa-r into theformation, as otherwise those parts of the formation directlysurrounding the well will not be consolidated. Therefore a fluid havingplastering properties (such as a mud slush) is suitably used as drivemedium, as such fluid will form a substantially impermeable sheath onthe wall of the formation directly after the resin solution has beenforced into the formation, whereby any further displacement of the resinsolution in the formation will be prevented. An alternative is the useof a gel plug or a As the resin solution should be mechanical plugbetween the resin solution and the drive fluid. When such a plug isemployed, the drive fluid may be any desired liquid, e.g., crude oil orsalt water.

ILLUSTRATIV E EXAMPLES In the following examples, the epoxy compound isof the type prepared from 2,2-bis(4hydroxyphenyl)propane andepichl-orohydrin as described in U.S. 2,633,458 under the headingPolyether A; it has an epoxy value of about 0.54 eq./.100 g., an epoxideequivalent about 185, an average molecular weight of about 380, and aviscosity at 25 C. in the range from 100 to 160 poises. rlhe hydrocarbonsolvent is the above-described hydrocarbon mixture boiling between 370and 510 F. and having a content of aromatic hydrocarbons in excess of Inthe final solutions the combined concentration of epoxy compound andcuring agent is about 18 percent by volume.

In the tests, a mass of surface sand having a mean particle size of 0.1millimeter was consolidated at various curing temperatures by a solutionof the compositions shown in Table 1.

TABLE 1 Curing agent: Bis(3-metbiyl-4-almirnocyclohexyl) methane, vo-l.percent Epoxy compound: Defined in text, vol. percent" 12 Solvent:Defined in text, vol. percent 72-82 Reaction retarder: Acetone, vol.percent 0-10 Resin separation promoter: Phenol, g./l. 3

The volume ratio of curing agent to polyepoxide was 0.5; this ratio,Iwhile keeping the combined concentration of curing agent and epoxycompound in the solution constant (in this case 18 Vol. percent) hadbeen found to give maximum compressive strength of the mass afterconsoldation thereof.

The above solution contained 3 grams phenol per liter to ensure thetotal separation of the epoxy resin from the solution. Use of phenol forthis purpose can be dispensed with when using curing agents other thanbis(3-rnethyl-4aminocyclohexyl)methane In the tests, the influence ofpercentage of acetone in the epoxy compound/curing agent solution on theIRS time was determined at a temperature of C. The results are shown inTable 2, below.

In the above tests, the compressive strength of the resultingconsolidated mass as measured at 90 C. was between and 160 kilograms persquare centimeter.

The results, as indicated in Table 2, show that by the use of acetonethe time available for injecting the epoxy resin and curing agentsolution for treating permeable masses has been markedly extended.

In a further study, the effect of curing temperature on the IRS time wasdetermined. The resin solution composition was as in the previousexample, except for the concentration of phenol, which was varied withtemperature in such a way that at each test temperature the solutioncontaining no acetone had an IRS time of 2 hours. The results, shown inTable 3, indicate that the time extension which can be achieveddecreases at higher curing temperatures, but is still significant at 100C.

a By interpolation.

In a similar study, a solution was prepared withl-cyclohexylamino-3-aminopropane as curing agent. Expenments carried outat 80 C. curing temperature resulted in very similar IRS timeextensions, as shown 1n Table 4.

TABLE 4 Acetone (vol. IRS Time percent) Extension, percent,

at 80 C.

By extrapolation.

The compresisve strength can be increased by increasing theconcentration of the curing agent and the epoxy compound in the solutionwhile maintaining their ratio constant. This increase in concentrationis accompanied by an increasing reduction of permeability. In the abovetests, the permeability reduction lies within the range of 30% to 40%.

A preferred method of practicing the present invention in consolidatingan underground formation with retention of permeability will now bedescribed by way of example.

In an oil well in which the oil-producing formation consists of anunconsolidated sand, the formation conditions such as temperature andinjectivity are measured. Samples of the formation sands may be takenfor the purpose of measuring, inter alia, the water saturation.

From the pump capacity and the depth as well as the injectivity orpermeability of the formation, the minimum lrequired initial resinseparation time, which at least equals the time required to pump theresin solution down to the formation, can be calculated.

From laboratory test results such as those in Table 2, the requiredpercentages of the epoxy compound, curing agent, ketone, phenol, ifused, and solvent are determined, which give an initial resin separationtime which at the temperature of the earth formation is sullcient topermit pumping the solution down into the formation without encounteringpremature separation of resin from the solution.

The required proportions of epoxy compound, curing agent, ketone forretarding the rate of reaction between curing agent and epoxy compoundto the desired degree, and phenol, if used, are subsequentlydissolvedfin the solvent. The phenol should be mixed with the epoxycompound/ curing agent solution only just before the solution is pumpedinto the borehole.

Referring now to the drawing, FIG. 1 shows a well borehole which hasbeen drilled through various strata, including a formation or formationshaving an oil producing zone 12. Well casing 13 is shown traversing oilzone 12. Dependent in the casing is a tubing string 14 which isperforated at the lower end thereof with perforations 23 and whichcarries straddle packers 21 and 22, capable of isolating a section ofthe borehole within the oil bearing formation 12. Within said isolatedsection, the casing is perforated with perforations 24, so that thetubing is in liquid communication with the oil bearing formation.

After the required preparations have been made as described, anoil-displacing fluid, e.g., diesel oil `or a diesel oil-aromaticsmixture, may be pumped down through tubing 14 and into the oil bearingformation. Following this there may be pumped down a water-displacingfluid, e.g., isopropyl alcohol, and then a spacer fluid, e.g., the samehydrocarbon composition used as solvent for the resin. Finally there ispumped into the formation the freshly prepared resin solution ofpredominantly aromatic hydrocarbons containing dissolved therein apolyepoxide, the amine curing agent, and a ketone as cure retarder, allas described above.- The resin solution is followed by a drive fluid.

The Ioil displacing fluid is used where the oil in the formation isrelatively viscous. This fluid dilutes the oil and facilitates itsdisplacement from the pore-space to be treated.

The water-removing fluid dissolves or emulsies the connate wateradhering to the grains of the formation. Thereafter, the spacer-fluid`drives out the solution or emulsion of water in the water-removingfluid; the spacer fluid is followed by the resin solution.

FIG. 1 illustrates the situation after `all described liquids have beenpumped down through tubing 14 and into oil zone 12 and drive fluid 25,e.g., mud slush, has just reached the Walls of the casing. As shown inFIG. 1, the portion of the oil Zone nearest the well borehole has thepores between sand grains of the formation filled with resin solution16. Immediately outside the Zone containing the resin solution there isa zone into which spacer liquid 18 has been displaced. Still further outare the zones containing water-displacing liquid 1.9 and oil-displacingliquid 20. At this stage further pumping into the formation isdiscontinued and the well is shut in for a period such as, for example,24 to 36 hours, to permit the resin to precipitate from the solution andharden on the sand grains of the formation. Thereafter the well isopened, permitting the remaining solvent, spacer liquid,water-displacing liquid and oil-displacing liquid to be withdrawn backinto the borehole and up through the tubing, either by virtue of thenatural pressure of fluids in the formation or by pumping, as required.

FIG. 2 illustrates the same well as FIG. 1, after the well has beenplaced in operation. The several fluids, including the remaining liquidcomponents of the resin solution, have been withdrawn back up throughtubing 14 and oil 26 is now being produced from formation 12 and removedthrough the tubing. Zone 25 shows the area which had contained the resinsolution. In this area the sand grains which were previouslyunconsolidated are now rmly bound together by cured resin. The strengthof this zone continues to increase for several days after completion ofthe treatment, and ultimately reaches a plateau of strength whichappears to be permanent.

The method of plugging a formation according to this invention isillustrated by reference to FIG. 3 of the drawing.

In the drawing a well borehole 111 is shown which has been drilledthrough various strata, including non-porous formations 112 and 113 anda porous water bearing formation 114. A well casing 115 is showncemented in the upper portion of tlhe well ending in non-porousformation 112. A drill string 116 is placed in the well, terminating indrill bit 117. The well is capped as indicated schematically by cap 118.

After the required preparations have been made as described, water isintroduced into the well through tubing 116 until pumping pressuresindicate that the water column in the borehole is remainingsubstantially static and water is entering the formation 114. Theprepared resinforming solution, having a composition calculated to setup as a gel rather than depositing liquid resin on the sand particles,is then pumped into the well and enters the formation. The drawingillustrates that stage of the operation at which a head of water, 121,is in the borehole while part of resin-forming solution 122 has enteredthe formation and some is still in the borehole and in the drill string.A displacing iiuid, 123, such as crude oil or mud slush, or a gel plugfollowed by a displacing fluid, is in the drill string above theresin-forming solution.

After the desired amount of resinforming solution has been introducedinto the formation, 4the drill string is raised above the level of resinsolution in the well and the well is kept shut in until the resinsolution has set up as a solid .gel and cured to sufficient hardness towithstand the formation pressure. The remaining resin plug in theborehole can then be drilled out, and further drilling of the wellresumed.

It will be readily apparent that numerous other methods for introducingthe required solutions into earth formations can be applied. Forexample, it is sometimes desirable to place a casing string in theborehole, seal the casing string in the -borehole along the length ofthe string passing through the formation to be treated, form a channelthrough the string and into the permeable section of the formation andthen inject the treating solution in the manner previously describedthrough the channel so formed into the permeable formation. Detailsconcerning such a method of injecting treating solutions in general intoa formation are given, for example, in copending patent application169,016 to Prats et al., filed January 26, 1962, and now abandoned.

When only a small portion of formation is to be treated, a specialtool-may be employed in which each solution, i.e., water displacing uidand treating solution, is contained in a separate compartment. The toolis lowered on a wireline to the desired depth, the casing and forma'-tion are penetrated if necessary, the solutions are forced from the toolinto the formation in the desired sequence, and the well is shut in forthe time required for the resin to precipitate and harden. This systempermits use of the solution employing the curing agent of this inventionin formations characterized by extremely high temperatures, at which theIRS is short.

Still other methods of injecting the desired treating solutions into theformation to be treated will occur to the person skilled in the art.

The following illustrates the application of the method of thisinvention to consolidation of sand surrounding an Qil well, whileretaining permeability. The oil-producing formation is a clean, welldeveloped, sand Stringer in the Miocene N series. An analysis of sidewall samples, which are loosely consolidated very line to fine grainsand, indicates that the sand contains approximately clay, such askaolinite and montmorillonite. The interval to be consolidated in thewell is a 9-foot stringer, of which 6 feet is perfor-ated. The bottomhole temperature is 90 C.

Prior to preparing the resin solution, the initial resin separationtimes for solutions of 12% of polyepoxide and 6% of-bis(3-methyl-4-aminocyclohexyl)methane in hydrocarbon solvent withvarying amounts of acetone are determined at 90 C. In this instance, theinformation is presented in Table 2, above. The well crude oil being notcompletely soluble in diesel oil, a 50-50 blend of diesel oil andaromatic kerosene extract is used as a first wash in the well treatment.This blend dissolves all the components of the crude.

The treatment is designed to consolidate a cylinder 3 feet in radius and9 feet in depth, the entire thickness of the sand Stringer. The sand isfirst washed with 3 pore volumes of the blend of diesel oil and keroseneextract. This is followed by an equal volume of isopropyl alcohol toremove any remaining water from the formation. Half a volume of dieseloil-kerosene extract is then pumped down as spacer. The resin solutionmixed to have an initial resin separation time sufficient to permit itto be pumped into the formation. About 1.1 pore volume of the resinsolution is placed into the formation. Care is taken that the resinsolution is just displaced into the formation without penetrating toofar and without retaining any resin solution in the well bore itself.The well is then shut in for 24 hours.

When pressure is released on the well, the fluids begin to unloadimmediately. Thus swabbing is not required to bring the well intoproduction. On a l-hour production test only 0.2% B S. shakeout isobtained. Although similar sand has been eifectively retained by othermethods not involving epoxy resin solutions, those wells have producedlarge amounts of sand during cleanup until lbridging occurs. This Wellproduces sand free immediately. Sand free production is thereafterobtained.

We claim as our invention:

1. In the method of treating a permeable earth formation which comprises(a) preparing a solution comprising a solvent, a resinformingpolyepoxide and a curing agent for said polyepoxide;

(b) injecting said solution into said formation; and

(c) retaining said solution in said formation for a sufficient time topermit the resulting epoxy resin to adhere to the sand grains of saidformation and cure to a hard, cross-linked, hydrocarbon-insoluble resin;

the improvement which comprises preparing as said solution a mixture of:

(1) a hydrocarbon solvent consisting of a mixture of at least 50 percentby weight of aromatic hydrocarbons, the remainder beingsaturatednon-aromatic hydrocarbons, wherein the ratio of said types ofhydrocarbons is predetermined to maintain the reaction product of saidresin and curing agent in solution for the period of time required toinject said solution into said formation;

(2) a resin-forming polyepoxide;

(3) a hydrocarbon-soluble amine curing agent for said polyepoxide; and

(4) a lower aliphatic ketone; in proportions selected such that:

(i) the total amount of said hydrocarbon solvent is between 30 and 95percent by volume of said solution;

' (ii) the total amount of polyepoxide and curing agent is between 3 and50 percent by volume of said solution; and

(iii) the composition of said solution is predetermined to maintain thepartial reaction product of said polyepoxide and said curing agentdissolved for the time required to inject said solution into saidformation.

2. The method of consolidating an at least substantially unconsolidatedearth formation according to claim 1, wherein the total concentration ofpolyepoxide and curing agent is in the range from 5 to 20 percent byvolume of said solution and the composition of said solution ispredetermined to cause the partial reaction product of said polyepoxideand curing agent to precipitate from solution -as a liquid, adhere tothe sand grains of said formation and cure, in such manner that asubstantial proportion of luhe permeability of said formation -isretained.

3. The method of plugging a permeable earth formation according to claim1, wherein the total concentration of polyepoxide and curing agent is inthe range from 20 to 50 percent by volume of said solution and thecomposition of said solution is predetermined to cause the solutionwhich contains the partial reaction product of said polyepoxide andcuring agent to set up as a gel within the pores of said formation insuch a manner that the pores-space of said formation is filled and nopermeability is retained.

4. The method according to claim 2 wherein said solution comprises (1)hydrocarbon solvent which contains at least 80 percent by weightaromatics and boils in the range from 350 to 650 F.;

(2) normally liquid polyepoxide which is the product of the reaction of2,2bis(4hydroxyphenyl) propane and epichlorohydrin in an alkalinemedium;

(3) Ia polyamine containing at least one siX-membered carbocyclic ringwherein at least one amino group selected from unsu-bstituted andalkyl-substituted primary and secondary amino groups is attacheddirectly to a cycloaliphatic ring; and

(4) acetone.

5. The method `according to claim 4 wherein said earth formation, priorto treatment, contains connate water, and wherein said Water isdisplaced from said formation by forcing a water-displacing liquid intosaid formation prior to said resin-forming solution.

6. The method according to claim 4 wherein said earth formation containsconnate water and is penetrated by a borehole, and wherein there areforced into a portion of said formation surrounding said borehole,through suitable perforations, in sequence:v

(1) a crude-oil-displacing uid;

(2) a water-displacing fluid;

(3) a spacer uid; and

(4) said resin-forming solution; and said formation is then shut in forthe time required by the reaction product of the polyepoXide and curingagent to cure to a hard, cross-linked, hydrocarbon-insoluble resin. l

7. The method of consolidating an interval of a permeable, at leastsubstantially unconsolidated earth formation which is at a temperaturein the range from 80 to 120 C., contains connate water, and is in uidcornmunication with a borehole, which comprises:

(a) preparing a solution of resin-forming polyepoxide and amine whichmaintains a viscosity below 100 centipoises at least until it enterssaid formation, said solution comprising (1) about 68 to about '82percent by volume of a hydrocarbon solvent which boils in the range from350 to 650 F. and which contains at least 80 percent by weight aromatichydrocarbons, the remainder being saturated hydrocarbons;

(2) about 12 percent by volume of a normally liquid polyepoxide which isthe product of the 14 reaction of 2,2-bis(4-hydroxyphenyl)propane andepichlorohydrin in an alkaline medium, and which has a molecular weightin the range from about 350 to 400 and an epoxy equivalent in therangefrom about 1.75 to 2.1;

(3) about 6 percent by volume of bis(3methy1 4-aminocyc1ohexyl) methane;(4) about 0.10 to 10 percent by volume of acetone; and (5) 4up to 4percent by volume of phenol; in proportions selected such that thepartial reaction product of said polyepoxide and said amine remainsdissolved for the time required to inject said solution into saidformation;

(b) isolating a zone of said borehole adjacent the formation interval tobe treated,

(c) pumping into said formation interval through said isolated zone ofsaid borehole a crude-oil-displacing fluid,

(d) thereafter pumping into said formation interval through saidisolated zone of said borehole isopropanol as water-displacing fluid,

(e) thereafter pumping said resin solution into said formation intervalthrough said isolated zone of said borehole,

(f) retaining said solution in said formation for a suicient time topermit partially cured epoxy resin to separate from said solution,deposit on the sand grains of said formation as a thin surface layer andcure to a hard, cross-linked, hydrocarbon insoluble resin, and

(g) producing oil from said oil-bearing formation through saidconsolidated formation interval and said borehole.

References Cited by the Examiner UNITED STATES PATENTS 8/1963 Hilton etal. 166-33 3/1964 Robichaux 166-33

1. IN THE METHOD OF TREATING A PERMEABLE EARTH FORMATION WHICH COMPRISES(A) PREPARING A SOLUTION COMPRISING A SOLVENT, A RESINFORMINGPOLYEPOXIDE AND A CURING AGENT FOR SAID POLYEPOXIDE; (B) INJECTING SAIDSOLUTION INTO SAID FORMATION; AND (C) RETAINING SAID SOLUTION IN SAIDFORMATION FOR A SUFFICIENT TIME TO PERMIT THE RESULTING EPOXY RESIN TOADHERE TO THE SAND GRAINS OF SAID FORMATION AND CURE TO A HARD,CROSS-LINKED, HYDROCARBON-INSOLUBLE RESIN; THE IMPROVEMENT WHICHCOMPRISES PREPARING AS SAID SOLUTION A MIXTURE OF: (1) A HYDROCARBONSOLVENT CONSISTING OF A MIXTURE OF AT LEAST 50 PERCENT BY WEIGHT OFAROMATIC HYDROCARBONS, THE REMAINDER BEING SATURATED NON-AROMATICHYDROCARBONS, WHEREIN THE RATIO OF SAID TYPES OF HYDROCARBONS ISPREDETERMINED TO MAINTAIN THE REACTION PRODUCT OF SAID RESIN AND CURINGAGENT IN SOLUTION FOR THE PERIOD OF TIME REQUIRED TO INJECT SAIDSOLUTION INTO SAID FORMATION; (2) A RESIN-FORMING POLYEPOXIDE; (3) AHYDROCARBON-SOLUBLE AMINE CURING AGENT FOR SAID POLYEPOXIDE; AND (4) ALOWER ALIPHATIC KETONE; IN PROPORTIONS SELECTED SUCH THAT: (I) THE TOTALAMOUNT OF SAID HYDROCARBON SOLVENT IS BETWEEN 30 AND 95 PERCENT BYVOLUME OF SAID SOLUTION; (II) THE TOTAL AMOUNT OF POLYEPOXIDE AND CURINGAGENT IS BETWEEN 3 AND 50 PERCENT BY VOLUME OF SAID SOLUTION; AND (III)THE COMPOSITION OF SAID SOLUTION IS PREDETERMINED TO MAINTAIN THEPARTIAL REACTION PRODUCT OF SAID POLYEPOXIDE AND SAI CURING AGENTDISSOLVED FOR THE TIME REQUIRED TO INJECT SAID SOLUTION INTO SAIDFORMATION.